package com.hery.utils;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Map;
import java.util.TreeMap;

/** A driver that is used to run programs added to it
 */

public class ProgramDriver {

    /**
     * A description of a program based on its class and a
     * human-readable description.
     * @date april 2006
     */
    Map<String, ProgramDescription> programs;

    public ProgramDriver(){
        programs = new TreeMap<String, ProgramDescription>();
    }

    static private class ProgramDescription {

        static final Class<?>[] paramTypes = new Class<?>[] {String[].class};

        /**
         * Create a description of an example program.
         * @param mainClass the class with the main for the example program
         * @param description a string to display to the user in help messages
         * @throws SecurityException if we can't use reflection
         * @throws NoSuchMethodException if the class doesn't have a main method
         */
        public ProgramDescription(Class<?> mainClass,
                                  String description)
                throws SecurityException, NoSuchMethodException {
            this.main = mainClass.getMethod("main", paramTypes);
            this.description = description;
        }

        /**
         * Invoke the example application with the given arguments
         * @param args the arguments for the application
         * @throws Throwable The exception thrown by the invoked method
         */
        public void invoke(String[] args)
                throws Throwable {
            try {
                main.invoke(null, new Object[]{args});
            } catch (InvocationTargetException except) {
                throw except.getCause();
            }
        }

        public String getDescription() {
            return description;
        }

        private Method main;
        private String description;
    }

    private static void printUsage(Map<String, ProgramDescription> programs) {
        System.out.println("Valid program names are:");
        for(Map.Entry<String, ProgramDescription> item : programs.entrySet()) {
            System.out.println("  " + item.getKey() + ": " +
                    item.getValue().getDescription());
        }
    }

    /**
     * This is the method that adds the classed to the repository
     * @param name The name of the string you want the class instance to be called with
     * @param mainClass The class that you want to add to the repository
     * @param description The description of the class
     * @throws NoSuchMethodException
     * @throws SecurityException
     */
    public void addClass (String name, Class mainClass, String description) throws Throwable {
        programs.put(name , new ProgramDescription(mainClass, description));
    }

    /**
     * This is a driver for the example programs.
     * It looks at the first command line argument and tries to find an
     * example program with that name.
     * If it is found, it calls the main method in that class with the rest
     * of the command line arguments.
     * @param args The argument from the user. args[0] is the command to run.
     * @throws NoSuchMethodException
     * @throws SecurityException
     * @throws IllegalAccessException
     * @throws IllegalArgumentException
     * @throws Throwable Anything thrown by the example program's main
     */
    public void driver(String[] args)
            throws Throwable
    {
        // Make sure they gave us a program name.
        if (args.length == 0) {
            System.out.println("An example program must be given as the" +
                    " first argument.");
            printUsage(programs);
            System.exit(-1);
        }

        // And that it is good.
        ProgramDescription pgm = programs.get(args[0]);
        if (pgm == null) {
            System.out.println("Unknown program '" + args[0] + "' chosen.");
            printUsage(programs);
            System.exit(-1);
        }

        // Remove the leading argument and call main
        String[] new_args = new String[args.length - 1];
        for(int i=1; i < args.length; ++i) {
            new_args[i-1] = args[i];
        }
        pgm.invoke(new_args);
    }

}